One thing that I'd recommend from personal experience is iterating the application just like you would your startup. Read
http://ycombinator.com/howtoapply.html and then reread your application. See where/if some of the things that he talks about are present in your application. When I first did this I was shocked to see that I did almost all of the things that he said that you shouldn't do. I went back and updated the app. Then I repeated the cycle a few times. Lastly, as my product developed and I described it to people, I learned where to focus and refined my description and ultimately went back and updated the app again. Not that I am an expert by any means, just my 2 cents.